High levels of adherence to antiretroviral therapy (ART) is critical for attaining HIV treatment goals, such as sustained suppression of plasma HIV RNA, decreased risk of developing drug resistance, improved quality of life, and reduced risk of HIV transmission. Commonly used methods to assess ART adherence include patient's self-report, pharmacy refill data, pill counts, medication event monitoring system (MEMS) caps, or analysis of drug levels in a biomatrix (e.g., plasma and hair). However, there is no gold standard and clinicians and researchers must resort to the most feasible and cost-effective methods possible, which may result in biased or inaccurate estimates of adherence. We seek an alternative approach, which is more objective than self-report, does not require laboratory assays or expertise in the interpretation of results, and can be conducted with less time and financial resources in a wide range of healthcare systems and research settings. Using mobile telephones, participants will take photos of their medication vials (demonstrating the refill date n the photo) and the contents of their medication vials/pillboxes and text these photos to the study's mobile telephone number on a monthly basis to assess adherence based on pharmacy refill dates and pill counts. In a formative phase with a small sample of participants, we will examine comprehensibility of the study protocol and procedures and establish accuracy of our adherence measures over a three-month period. In the main study, we will examine the use of text messaged photos of ART vials and contents of medication vials/pillboxes to estimate adherence based on pharmacy refill dates and pill counts over six months. The aims of our research project are to: (1) Assess the feasibility and acceptability of a novel method of estimating ART adherence using photographed and text messaged pharmacy refill dates; (2) Examine the feasibility and acceptability of a study where recruitment, consent, hair sample collection, text messaging, and exit interviews will all be conducted remotely; and (3) Explore the relationship between adherence calculated based on text messaged photos of pharmacy refill dates and pill counts to an objective measure using drug levels in hair. We hypothesize that our novel approaches to remotely estimate ART adherence using pharmacy refill dates and pill counts obtained via text messaged photos among people living with HIV will be feasible, acceptable, and accurate. If feasible and acceptable, this method of estimating ART adherence can be used in clinical practice or for intervention studies where ART non-adherence can be detected early on, which can potentially help to minimize risk of virologic failure, decrease the risk of disease progression, and reduce transmission of drug- resistant virus. Additionally, the assessment of the feasibility and acceptability of an entirely remote research methodology is important for future research projects where stigma or physical transportation may be a significant barrier to participation. We will use these data to inform the proposed methods in subsequent large- scale adherence trials.